Chrome spawns one thread for each tab, extension and plug-in in addition to a "Browser" thread and a "GPU Process" thread. A summary of the processes is provided in Chrome's task manager (Shift + Esc or right-click on Chrome's chrome and select Task Manager).
Chrome uses significantly more resources than Firefox however it does not suffer from the horrid memory leaks that have plagued Firefox for years:
Mozilla Gets "Tough" on Firefox Memory Leaks
As the article states, the memory leaks are a well-known problem. It's an issue that the developers do not seem to be able to fix.
Chrome's performance is exceptional and stable. Firefox's performance is also exceptional at first launch but it can degrade in a matter of minutes to a choppy, annoying experience. If you're using Firefox and haven't already done so, try the Memory Restart add-on. Be sure to display the add-on bar to watch the memory inflate. In my experience, performance starts to degrade around 600 MB.
In a world where RAM is dirt cheap, Chrome is welcome to all it wants to use as long as it maintains its performance. I have 8 GB of RAM installed and rarely see total usage beyond 3 GB.
I switched to Chrome yesterday after at least five years of primary Firefox usage. I'm a bit sad to leave Firefox behind, but I had tired of restarting it four or five times a day just to keep the memory in check.
Ironically, it was the Google toolbar that had kept me tied to Firefox for the last year. I'm now using the Context Search extension in Chrome to achieve similar functionality to the Google toolbar "buttons" in Firefox.